The present invention relates to a front vehicle-body structure of a vehicle, and in particular, relates to the front vehicle-body structure of the vehicle comprising a pair of inside crash cans supporting a bumper reinforcement and a pair of outside crash cans provided on an outward side, in a vehicle width direction, of the pair of inside crash cans.
Conventionally, a technology for reducing an impact energy against a passenger in a vehicle frontal collision, in which a pair of right-and-left cylindrical crash cans are provided between respective front end portions of a pair of right-and-left front side frames extending in a vehicle longitudinal direction and a bumper reinforcement extending in a vehicle width direction, and the above-described crash cans are configured to have buckling (crush) deformation in a direction of its axial center in an initial stage of the collision, whereby the impact energy in the collision's initial stage can be absorbed, is known.
In general, the above-described crash cans are attached to respective front end portions of the pair of right-and-left front side frames via a pair of right-and-left set plates. Each of the pair of right-and-left set plates comprises two plates. Herein, one of these two plates which is located on the side of a bumper and connected to a rear end portion of the crash can, i.e., a bumper-side set plate, is fastened to the other plate which is located on the side of a vehicle body and connected to the front end portion of the front side frame, i.e., a vehicle-body-side set plate with bolts which are arranged longitudinally. Accordingly, the crash can which has got broken in a low-speed vehicle collision or the like is replaceable by a new one by removing the bolts, so that the reparability can be ensured.
Meanwhile, the above-described structure in which the bumper-side set plate is fixedly fastened to vehicle-body-side set plate with bolts, i.e., the cantilever structure of supporting at a so-called joint face, has a problem in that since the bumper reinforcement having a heavy weight and the crash cans tend to easily vibrate vertically which are caused by traveling vibrations of the vehicle, the NVH (Noise Vibration Harshness) performance of the vehicle body may decrease improperly, so that the passenger's habitability in a vehicle compartment may deteriorate. Accordingly, various technologies to improve the NVH performance by changing the natural frequency of a vehicle-body front portion have been proposed.
In a front vehicle-body structure of a vehicle disclosed in Japanese Patent Laid-Open Publication No. 2011-255815, there are provided a first set plate which is connected to a front end portion of a front side frame and a second set plate which is connected to a rear end portion of a crash can and capable of being fastened to the first set plate with bolts, and the first and second set plates respectively have a rigid joint portion where protrusion portions thereof are contacted and bolt-fastened to each other and a flexible joint portion where they are joined to each other via a damping member.
In the vehicle frontal collision, the impact energy acts on a vehicle-body portion on the outward side, in the vehicle width direction, of the front side frame. In this small-overlap collision (hereafter, referred to as “SOL collision”), the transmission efficiency of the impact energy to the front side frame decreases, compared to a collision case in which a collision object and the front side frame overlap each other, so that the amount of the impact energy's absorption which is caused by deformation of the front side frame decreases, and the impact energy transmitted to the vehicle-body side increases accordingly. Therefore, in order to increase the amount of the impact energy's absorption, taking measures of the SOL collision, an outside crash can is newly provided on the outward side, in the vehicle width direction, of the existing crash can (hereafter, referred to as the “inside crash can”).
According to the above-described front vehicle-body structure of the vehicle of the patent document, the properly-high joint force can be maintained by the rigid joint portion and also the vibration energy can be properly absorbed as the strain (distortion) energy by the flexible joint portion. However, this front vehicle-body structure of the vehicle of the patent document has a problem in that additional forming processes for forming storage portions to store the protrusion portions and the damping member therein at both the first and second set plates become necessary and also the parts number increases because of an addition of the damping member, so that there still exists a room for improvement in the productively.
Further, in a case in which the above-described outside crash can is newly provided for countermeasures of the SOL collision, the first and second set plates for attaching the outside crash can become necessary, and also forming processes and the damping member for the outside crash can increase, in addition to the above-described increase for the inside crash can, so that there is a concern that the productivity further deteriorates.